Cataracts in retired actinide-exposed radiation workers

Evaluation of X-ray protective goggles in mitigating eye lens radiation exposure during radiopharmaceutical handling and patient care in nuclear medicine

The aim of this study is to estimate eye lens exposure dose when handling radiopharmaceuticals and interacting with patients receiving radiopharmaceuticals, and to verify the usefulness of X-ray protective goggles in mitigating such radiation exposure using phantoms. To evaluate radiation exposure during the handling of radiopharmaceuticals, we employed a fluorescent glass dosimeter to measure the radiation doses associated with 99mTc, 123I, 131I, 111In, and 18F at distances of 30 cm and 60 cm, followed by calculation of the 3 mm dose equivalent rate (3DER). We then estimated the dose reduction rates for various scenarios, including the use of syringe shields and X-ray protective goggles with lead equivalences of 0.07, 0.15, 0.75, and 0.88 mmPb, as well as their combined application. X-ray protective goggles with lead equivalence of 0.75 mmPb outperformed those with 0.07 mmPb and 0.15 mmPb, for all radionuclides and at both source distances. X-ray protective goggles with 0.88 mmPb outperformed those with 0.75 mmPb during handling of 131I and 111In at a distance of 30 cm. In the remaining scenarios, X-ray protective goggles with 0.88 mmPb resulted in marginal reductions or no discernible additional effects. The overall shielding effect of X-ray protective goggles was less pronounced for 131I and 18F, but the combined use of a syringe shield with X-ray protective goggles with 0.75 or 0.88 mmPb improved the dose reduction rate for all scenarios. In simulating patient care, X-ray protective goggles with 0.88 mmPb demonstrated a dose reduction effect of approximately 50% or more. X-ray protective goggles could reduce the 3DER for the eye lens, and were more effective when combined with a syringe shield. It is valid to use a lead equivalence of 0.88 mmPb to fully harness the protective capabilities of X-ray shielding goggles when dealing with all five types of nuclides in clinical settings.

[Improved Protective Equipment for NICU Portable Radiography]

We have been developing protective equipment for portable radiography in neonatal intensive care units because the portable radiography's X-ray tube is in close proximity to the head of the nurse who is assisting the patient. Although our initial protective-equipment design was highly effective, there were some concerns that it obstructed the view of the patient and was difficult to handle. To overcome this problem, we have developed two new types of protective device: a narrow-type 0.13 mmPb device, 17 cm long and 45 cm wide (weight 200 g); and a wide type with a wider core material, 45 cm long and 25 cm wide (weight 300 g), both of which can be hung from the collimator cover of mobile X-ray equipment. The measured protective effectiveness was 80.6% at head height for the wide type and 76.8% for the narrow type. A survey of nurses regarding the new protective devices revealed no significant differences between the two types in terms of visibility and whether the devices would be an obstacle when assisting patients. The nurses preferred the wider type, which offered better protection. Radiological technologists also liked that both types were easy to handle because the irradiation field could be adjusted even after the device was fitted. Both types of the new protective device are thus expected to be useful in clinical practice in terms of their high protective effect and improved ease of handling.

[Creation of Protective Equipment for Portable Radiography in Neonatal Intensive Care Unit]

Portable imaging in the NICU requires the assistance of a nurse, and the nurse is in close proximity to the X-ray tube, In all, 64 percent of our nurses thought that additional protective equipment was needed. Therefore, a radiation protection device was created and its usefulness was verified. A protective equipment of 0.13 mmPb with a width of 38 cm and a length of 70 cm was made and hung from the mono-tank X-ray unit of the mobile X-ray unit. The position of the nurse was set at 30 cm outward from the center of the irradiation field, and the protective effect was measured at three points: (a) the patient's height, (b) 30 cm above the patient, and (c) 60 cm above the patient. For the imaging conditions, a 2-liter plastic bottle filled with water was placed in the incubator, and measurements were taken with an SID of 100 cm, irradiated field of 20.3 cm×25.4 cm, tube voltage of 58 kV, and tube current-time product of 10 mAs, which was converted to the actual imaging condition of 1 mAs. Based on the results obtained, a questionnaire survey was conducted on nurses' thoughts for the protective equipment created for them. Only 3% reduction in height of (a) where no protective equipment is reached but (b) 50% and (c) 92%, respectively. In all, 82 percent of the nurses had a favorable impression of the new protective equipment. It is expected that the protective equipment designed to control lens dose and reduce anxiety of nurses will be useful.

[Usefulness of Radiation Protection Cloths in Fluoroscopy with Clean Areas]

Lowering the dose limit for the lens of the eye incorporated into the Regulation on Prevention of Ionizing Radiation Hazards, effective on April 2021, and dose reduction will become more and more important in the field of radiation. Radiation protective cloth is used as a protective equipment in fluoroscopy rooms. Although it is usually used to protect staff from radiation exposure during endoscopic retrograde cholangiopancreatography, we investigated whether there is a way to use it for procedures in clean areas. Assuming ureterostomy fistula replacement in urology, the protective cloth was suspended on the side of the patient's head and posterior aspect of the tube, and the distance between the anterior aspect of the X-ray tube and the patient's foot was 55 cm. As a result of measuring the dose rate, a 10% dose reduction was obtained for the lens of the eye of the surgeon, and the distribution of air dose rate in the examination room was significantly reduced. Although scattered radiation from the radiation protection cloth appeared in some areas, the radiation dose to the patient was reduced throughout the body, and a high degree of radiation protection was obtained, especially for the lens of the eye. It is expected that the radiation protection cloths may be useful even when the length of the cloths is limited due to the cleanliness of the area.

[Calculation of Lens Exposure Reduction Using Organ-effective Modulation in Pediatric Head CT]

PURPOSE

Using a pediatric head phantom constructed in our department, we examined a method to reduce exposure by using organ-effective modulation (OEM; Toshiba Medical Systems Corporation, Tochigi) to tilt the gantry during pediatric head computed tomography (CT) scanning.

METHOD

The radiation reduction and CT image standard deviation (SD) were measured at gantry angles at which the orbit was slightly irradiated, partially irradiated, and completely irradiated. The OEM incident surface dose reduction rate was measured using an automatic exposure control (AEC) phantom with a diameter of 6-18 cm.

RESULTS

The lens surface dose reduction rate using OEM was 21.2%. When the gantry was tilted and the orbit was completely out of the scanning range, the rate of reduction was 47.8%. OEM incident surface dose reduction rates were 27.4% for a phantom diameter of 18 cm, 22.0% for that of 16 cm, 17.8% for that of 14 cm, 17.2% for that of 12 cm, 8.4% for that of 10 cm, and 0% for that of 8 cm and 6 cm. OEM effectiveness decreased with decreasing phantom diameter. The use of OEM increased the rate of change of SD by 1.25´ when the gantry inclination was 0°, 1.27´ when the gantry inclination was 10°, and 1.27´ when the gantry inclination was 20°in the 12 o'clock position.

CONCLUSION

The degree of reduction in exposure dose to the lens in pediatric head CT imaging was 47.8% by completely removing the lens from the irradiation range using gantry tilt and 21.2% by using OEM. The effect of OEM changed in proportion to tube current. The exposure reduction effect of the OEM decreases with decreasing head size, indicating its reduced effectiveness in head CT scans of smaller infants.

Ionising radiation and lens opacities in interventional physicians: results of a German pilot study

We assessed the feasibility of an epidemiological study on the risk of radiation-related lens opacities among interventional physicians in Germany. In a regional multi-centre pilot study associated with a European project, we tested the recruitment strategy, a European questionnaire on work history for the latter dosimetry calculation and the endpoint assessment. 263 interventional physicians and 129 non-exposed colleagues were invited. Questionnaires assessed eligibility criteria, risk factors for cataract, and work history relating to occupational exposure to ionising radiation, including details on type and amount of procedures performed, radiation sources, and use of protective equipment. Eye examinations included regular inspection by an ophthalmologist, digital slit lamp images graded according to the lens opacities classification system, and Scheimpflug camera measurements. 46 interventional (17.5%) and 30 non-exposed physicians (23.3%) agreed to participate, of which 42 and 19, respectively, met the inclusion criteria. Table shields and ceiling suspended shields were used as protective equipment by 85% and 78% of the interventional cardiologists, respectively. However, 68% of them never used lead glasses. More, although minor, opacifications were diagnosed among the 17 interventional cardiologists participating in the eye examinations than among the 18 non-exposed (59% versus 28%), mainly nuclear cataracts in interventional cardiologists and cortical cataracts in the non-exposed. Opacification scores calculated from Scheimpflug measurements were higher among the interventional cardiologists, especially in the left eye (56% versus 28%). Challenges of the approach studied include the dissuading time investment related to pupil dilatation for the eye examinations, the reliance on a retrospective work history questionnaire to gather exposure-relevant information for dose reconstructions and its length, resulting in a low participation rate. Dosimetry data are bound to get better when the prospective lens dose monitoring as foreseen by 2013 European Directives is implemented and doses are recorded.

The US Transuranium and Uranium Registries (USTUR): A Five-Decade Follow-Up Of Plutonium and Uranium Workers

Dedication: The research of the US Transuranium and Uranium Registries relies heavily upon postmortem autopsy findings and radiochemical analysis of tissues. The enormous debt owed to those now-deceased registrants who unselfishly voluntarily participated in the US Transuranium and Uranium Registries program through postmortem donation of their tissues and to those still-living registrants who have volunteered to be future postmortem tissue donors is hereby acknowledged with gratitude. The scientific findings derived from postmortem analysis of these tissues have been instrumental in advancing our understanding of the actinide elements in humans and have led to refinement, validation, and confidence in safety standards for those who work with these elements as well as for the general public. To these generous and anonymous persons who made this ultimate contribution, this paper is dedicated with great thanks and admiration.

Deterministic Effects to the Lens of the Eye Following Ionizing Radiation Exposure: is There Evidence to Support a Reduction in Threshold Dose?

Ionizing radiation exposure to the lens of the eye is a known cause of cataractogenesis. Historically, it was believed that the acute threshold dose for cataract formation was 5 Sv, and annual dose limits to the lens were set at 150 mSv. Recently, however, the International Commission on Radiological Protection has reduced their threshold dose estimate for deterministic effects to 0.5 Gy and is now recommending an occupational limit of 20 mSv per year on average. A number of organizations have questioned whether this new threshold and dose limit are justified based on the limited reliable data concerning radiation-induced cataracts. This review summarizes all of the published human epidemiological data on ionizing radiation exposure to the lens of the eye in order to evaluate the proposed threshold. Data from a variety of exposure cohorts are reviewed, including atomic bomb survivors, Chernobyl liquidators, medical workers, and radiotherapy patients. Overall, there is not conclusive evidence that the threshold dose for cataract formation should be reduced to 0.5 Gy. Many of the studies reviewed here are challenging to incorporate into an overall risk model due to inconsistencies with dosimetry, sample size, and scoring metrics. Additionally, risk levels in the studied cohorts may not relate to occupational scenarios due to differences in dose rate, radiation quality, age at exposure and latency period. New studies should be designed specifically focused on occupational exposures, with reliable dosimetry and grading methods for lens opacities, to determine an appropriate level for dose threshold and exposure limit.

Occupational exposure to low doses of ionizing radiation and cataract development: a systematic literature review and perspectives on future studies

Ionizing radiation is a well-known but little understood risk factor for lens opacities. Until recently, cataract development was considered to be a deterministic effect occurring at lens doses exceeding a threshold of 5-8 Gy. Substantial uncertainty about the level and the existence of a threshold subsists. The International Commission on Radiation Protection recently revised it to 0.5 Gy. Based on a systematic literature review of epidemiological studies on exposure to low levels of ionizing radiation and the occurrence of lens opacities, a list of criteria for new epidemiological studies was compiled, and a list of potential study populations was reviewed. Among 24 publications finally identified, six report analyses of acute exposures in atomic bomb survivors and Chernobyl liquidators, and the others report analyses of protracted exposures in occupationally, medically or accidentally exposed populations. Three studies investigated a dose threshold: in atomic bomb survivors, the best estimates were 1 Sv (95 % CI <0-0.8 Sv) regarding lensectomies; in survivors exposed as children, 0.6 Sv (90 % CI <0.0-1.2 Sv) for cortical cataract prevalence and 0.7 Sv (90 % CI 0.0-2.8 Sv) for posterior subcapsular cataract; and in Chernobyl liquidators, 0.34 Sv (95 % CI 0.19-0.68 Sv) for stage 1 cataract. Current studies are heterogeneous and inconclusive regarding the dose-response relationship. Protracted exposures and high lens doses occur in several occupational groups, for instance, in physicians performing fluoroscopy-guided interventional procedures, and in accidentally exposed populations. New studies with a good retrospective exposure assessment are feasible and should be initiated.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Radiation cataractogenesis: a review of recent studies

The lens of the eye is recognized as one of the most radiosensitive tissues in the human body, and it is known that cataracts can be induced by acute doses of less than 2 Gy of low-LET ionizing radiation and less than 5 Gy of protracted radiation. Although much work has been carried out in this area, the exact mechanisms of radiation cataractogenesis are still not fully understood. In particular, the question of the threshold dose for cataract development is not resolved. Cataracts have been classified as a deterministic effect of radiation exposure with a threshold of approximately 2 Gy. Here we review the combined results of recent mechanistic and human studies regarding induction of cataracts by ionizing radiation. These studies indicate that the threshold for cataract development is certainly less than was previously estimated, of the order of 0.5 Gy, or that radiation cataractogenesis may in fact be more accurately described by a linear, no-threshold model.